Novel photographic products and processes

ABSTRACT

The present invention relates to photography, particularly, to photographic products specifically adapted for employment in specified photographic diffusion transfer color processes and, more particularly, to photographic products which comprise a fixed or permanent composite photosensitive structure including, as essential layers, in sequence, a first dimensionally stable layer transparent to actinic radiation; a first polymeric layer dyeable by a diffusion transfer process dye image-forming material; a processing composition permeable opaque layer; a photosensitive silver halide layer having associated therewith a diffusion transfer process dye image-forming material; a second polymeric layer dyeable by a diffusion transfer process dye image-forming material; a second dimensionally stable layer transparent to actinic radiation; means for providing opacifying agent intermediate the second dyeable polymeric layer and the next adjacent photosensitive silver halide layer; and means for providing a diffusion transfer process processing composition preferably intermediate the second dyeable polymeric layer and the next adjacent photo-sensitive silver halide layer; and to specified photographic diffusion transfer color processes employing such products.

States Patent [191 Unite eid [ Sept. 17, 1974 NOVEL PHOTOGRAPHIC PRODUCTS AND PROCESSES Jerome L. Reid, Wayland, Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

Mass.

[22] Filed: Mar. 23, 11973 [21] Appl. No.2 344,166

[75] Inventor:

Primary ExaminerRonald H. Smith Assistant Examiner-Richard L. Schilling Attorney, Agent, or Firm-Robert M. Ford [57] ABSTRACT The present invention relates to photography, particularly, to photographic products specifically adapted for employment in specified photographic diffusion transfer color processes and, more particularly, to photographic products which comprise a fixed or permanent composite photosensitive structure including, as essential layers, in sequence, a first dimensionally stable layer transparent to actinic radiation; a first polymeric layer dyeable by a diffusion transfer process dye image-forming material; a processing composition permeable opaque layer; a photosensitive silver halide layer having associated therewith a diffusion transfer process dye image-forming material; a second polymeric layer dyeable by a diffusion transfer process dye image-forming material; a second dimensionally stable layer transparent to actinic radiation; means for providing opacifying agent intermediate the second dyeable polymeric layer and the next adjacent photosensitive silver halide layer; and means for providing a diffusion transfer process processing composition preferably intermediate the second dyeable polymeric layer and the next adjacent photo-sensitive silver halide layer; and to specified photographic diffusion transfer color processes employing such products.

34 Claims, 9 Drawing Figures PATENTEDSEPI 1 m4 sum 5 0F 5 3,8363% NOVEL PHOTOGRAPHIC PRODUCTS AND PROCESSES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention'is directed to providing new and improved diffusion transfer color process photographic film units adapted to provide, as a function of the point-to-point degree of photoexposure, by diffusion transfer processing dye transfer image formation.

2. Description of Prior Art As disclosed in U.S. Pat. No. 3,672,890 a composite photosensitive structure, particularly adapted for reflection type photographic diffusion transfer color process employment, which comprises a plurality of essential layers including, in sequence, a dimensionally stable layer preferably opaque to incident radiation; one or more silver halide emulsion layers having associated therewith a diffusion transfer process dye imageproviding material; a polymeric layer adapted to receive solubilized dye image-providing material diffusing thereto; and a dimensionally stable transparent layer, may be exposed to incident actinic radiation and processed by interposing, intermediate the silver halide emulsion layer and the reception layer, a processing composition and an opactifying agent, which may reflect incident radiation, in a quantity sufficient to mask dye image-providing material associated with the silver halide emulsion.

In a preferred embodiment, the composite photosensitive structure includes a rupturable container, retaining an alkaline processing composition and the opacifying agent, fixedly positioned extending transverse a leading edge of the composite structure in order to effect, upon application of compressive pressure to the container, discharge of the processing composition intermediate the opposed surfaces of the reception layer and the next adjacent silver halide emulsion.

The liquid processing composition, distributed intermediate the reception layer and the silver halide emulsion, permeates the silver halide emulsion layers of the composite photosensitive structure to initiate development of the latent images contained therein resultant from photoexposure. As a consequence of the development'of the latent images, dye image-providing material associated with each of the respective silver halide emulsion layers is individually mobilized as a function of the point-to-point degree of the respective silver halide emulsion layers photoexposure, resulting in imagewise distributions of mobile dye image-providing materials adapted to transfer, by diffusion, to the reception layer to provide the desired transfer dye image. Subsequent to substantial dye image formation in the reception layer, means associated with composite structure are adapted to convert the pH of the film unit from a first processing pH at which dye image-providing material is diffusible as a function of the film units photoexposure to a second pH at which the transfer dye image exhibits increased stability, preferably a sufficient portion of the ions of an alkaline processing composition transfers, by diffusion, to a polymeric neutralizing layer to effect reduction in the alkalinity of the composite film unit from a first alkaline processing pH to the second pH at which dye image-providing material is substantially nondiffusible, and further dye imageproviding material transfer is thereby substantially obviated.

The transfer dye image is viewed, as a reflection image, through the dimensionally stable transparent layer against the background provided by the opacifying agent, distributed as a component of the processing composition, intermediate the reception layer and next adjacent silver halide emulsion layer. The thus-formed opacifying stratum effectively masks residual dye image-providing material retained in association with the silver halide emulsion layer subsequent to processing.

In U.S. Pat. No. 3,415,644, the dimensionally stable layer of the film unit next adjacent the photosensitive layer or layers is disclosed to be opaque, the opacifying agent is initially disposed in an aqueous alkaline processing composition and the film units pH modulating means are disclosed to comprise a polymeric layer disposed intermediate the dimensionally stable transparent layer and the reception layer and adapted to re duce, subsequent to substantial dye transfer image formation, the pH of an aqueous alkaline processing composition from a first processing pH at which the dye image-forming material or materials are soluble and diffusible in the composition as a function of the photoexposure of the photosensitive silver halide layer associated therewith to a second pH at which the dye image forming material or materials are substantially nondiffusible and, as disclosed in U.S. Pat. No. 3,415,646, the dimensionally stable layer of the film unit next adjacent the photosensitive silver halide layer or layers is disclosed to be transparent to incident actinic radiation and, as further disclosed in U.S. Pat. No. 3,415,645, in such instance the opacifying agent. may be initially dis posed in the film unit intermediate the reception layer and next adjacent silver halide layer.

As disclosed in U.S. Pat. Nos. 3,615,421 and 3,661,585, the opacifying component of the film unit may optionally be initially disposed as a preformed processing composition permeable layer, intermediate the reception layer and next adjacent silver halide layer, in a concentration which prior to photoexposure is insufficient to prevent transmission therethrough of exposing actinic radiation and which, subsequent to processing, possesses an opacifying capacity effective to mask residual dye image-providing material retained associated with the film units silver halide emulsion layers, and in U.S. Pat. No. 3,647,435, the opacifying component of the film unit may optionally be initially formed in situ, intermediate the reception layer and next adjacent silver halide layer, during photographic processing of the film unit.

In U.S. Pat. No. 3,647,437, the opacifying component is disclosed to optionally comprise a lightabsorbing reagent such as a dye which is present as an absorbing species at the first pH and which may be converted to a substantially non-absorbing species at the second pH, and in U.S. Pat. Nos. 3,473,925; 3,573,042 and 3,576,626, opacifying and reflecting component, respectively, may be individually interposed intermediate the silver halide layer and reception layer by selective distribution from a composite or a plurality of rupturable containers.

In U.S. Pat. No. 3,573,043, the polymeric neutralizing layer is disclosed to be optionally disposed interme diate the dimensionally stable opaque layer and next adjacent essential layer, i.e., next adjacent silver halide/dye image-providing material component, to effect the designated modulation of film units environmental pH; U.S. Pat. No. 3,576,625 discloses the employment of particulate acid distributed within the film unit to effect the modulation of the environmental pH, and U.S. Pat. No. 3,573,044 discloses the employment of processing composition solvent vapor transmissive dimensionally stable layers to effect process modulation of dye transfer as a function of solvent concentration.

Where desired, the film unit may also be constructed in accordance with the disclosure of U.S. Pat. Nos. 3,594,164; 3,594,165; 3,689,262 and 3,701,656 to comprise a composite photosensitive structure including a transparent dimensionally stable layer carrying a reception layer, a processing composition permeable opaque layer and a photosensitive silver halide layer and the film unit may include a separate dimensionally stable sheet element adapted to be superposed on the surface of the photosensitive structure opposite the dimensionally stable layer and may further include means such as a rupturable container retaining processing composition for distribution of a processing composition intermediate the sheet and photosensitive structure to effect processing. As further disclosed in certain of the last-cited patents and applications, in structures wherein the receptor is positioned next adjacent the transparent layer or the processing composition and/or the sheet is to be separated from the remainder of the film unit subsequent to processing, the latter elements may optionally include opacifying component.

As disclosed in U.S. Pat. No. 3,620,724, the dimensionally stable layer referred to may be opaque and in which instance the photosensitive silver halide layer is positioned next adjacent the opaque support layer and the opacifying component of the film units processing composition permeable opaque layer will be disposed in the unit in a concentration insufficient to prevent transmission therethrough of exposing actinic radiation and which, subsequent to processing, possesses an opacifying capacity effective to mask residual dye image-providing material retained associated with the silver halide layer, and as disclosed in U.S. Pat. No. 3,647,434, the opacifying agent may be optionally formed in such film unit, in situ, during processing of the unit.

As disclosed in British Pat. No. 874,046, two or more separate diffusion transfer process images may be simultaneously provided by exposure and diffusion transfer processing of a film unit which includes a transfer process image-receiving layer located contiguous one major surface of a silver halide emulsion and an imagereceiving element superposed contiguous the opposite major surface of the emulsion during processing and,

subsequent to processing, separating the imagereceiving element from its superposed relationship with the emulsion and, where required, the emulsion from its contiguous relationship with the image-receiving layer for viewing of the respective transfer images.

SUMMARY OF THE INVENTION The present invention is directed to novel photographic diffusion transfer color process film units and specifically to integral negative/positive, diffusion transfer process photographic film units adapted to provide, by diffusion transfer processing, photographic color image reproduction as a function of exposure of such film unit to incident actinic radiation.

In accordance with the present invention, the film units will comprise a plurality oflayers including, in relative order, a first dimensionally stable layer transparent to incident actinic radiation; 21 first transparent layer adapted to receive diffusion transfer process dye image-forming material diffusing thereto; one or more photosensitive silver halide layers having associated therewith one or more diffusion transfer process dye image-forming materials; an opaque layer; a second transparent layer adapted to receive dye image-forming material diffusing thereto and a second dimensionally stable layer transparent to incident actinic radiation; means for providing, intermediate the first reception layer and next adjacent silver halide layer, opacifying agent; and means for providing a processing composition in contact with the photosensitive layers, and, in a particularly preferred embodiment, a processing composition possessing a first pH at which the diffusion transfer process dye image-forming material is diffusible during processing and means for modulating the pH of the film unit from the first pH to a second pH at which dye image-forming material is substantially nondiffusible subsequent to substantial dye transfer image formation.

In accordance with a specifically preferred embodiment of the present invention, a film unit assemblage of the aforementioned general structural parameters will be adapted to be processed, subsequent to photoexposure, in the presence of actinic radiation and may be fabricated to employ, as opacifying agent interposed intermediate the first reception layer and next adjacent silver halide layer subsequent to photoexposure, an inorganic light-reflecting pigment dispersion containing reflecting pigment and at least one optical filter agent, at a pH above the pKa of the optical filter agent and at which pH the dye image-forming material is diffusible during processing as a function of silver halide layer photoexposure, in a concentration in admixture effective to provide a barrier to transmission of actinic radiation therethrough; the means for interposing the opacifying agent and the processing composition will comprise a rupturable container, retaining the opacifying agent disposed in the processing composition selected, fixedly positioned extending transverse a leading edge of the film unit and adapted, upon application of compressive pressure, to'distribute its contents intermediate the reception layer and next adjacent silver halide layer, and the means for modulating the pH of the film unit will be adapted to convert the unit to a second pH below the pKa of the selected optical filter agent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a fragmentary perspective view of one embodiment of a photographic film unit in accordance with the invention;

FIGS. 2, 4 and 6 are diagrammatic enlarged crosssectional views of the film unit of FIG. 1, along section line 2-2, illustrating the association of elements during the three illustrated stages of the performance of a diffusion transfer process, for the production of a multicolor transfer image according to the invention, the thickness of the various materials being exaggerated, and wherein FIG. 2 represents an exposure stage, FIG. 4 represents a processing stage and FIG. 6 represents a product of the process; and

FIGS. 3, 5 and 7 are diagrammatic, further enlarged cross-sectional views of the film unit of FIGS. 2, 4 and 6, along section lines 3-3, 5-5, and 7--7, respectively, further illustrating, in detail, the arrangement of layers comprising the photosensitive laminate during the three illustrated stages of the transfer process;

FIG. 8 is a perspective view of a film pack comprising an assemblage of film units; and

FIG. 9 is a longitudinal sectional view taken substantially midway between the sides of the film pack of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION As previously characterized, diffusion transfer photographic processing in accordance with the present invention may be employed to provide a positive reflection dye image, as a direct function of actinic radiation incident on a film unit assemblage which unit is preferably constructed to comprise a plurality of sequential layers including a first dimensionally stable layer transparent to incident radiation; a first transparent layer adapted to receive diffusion transfer process dye image-forming material diffusing thereto; one or more photosensitive silver halide layers having associated therewith one or more diffusion transfer process dye image-forming materials; an opaque layer; a second layer adapted to receive dye image-forming material diffusing thereto; a second dimensionally stable layer transport to incident radiation; means for interposing intermediate the first reception layer and the next adjacent silver halide layer opacifying agent, preferably an inorganic reflecting pigment dispersion containing at least one optical filter agent or dye, in a concentration effective to provide, subsequent to selective photoexposure of the silver halide layer, protection of the silver halide layer from further exposure to actinic radiation incident on the dimensionally stable layer; and means for converting the pH of the film unit from the first processing pH to a second pH at which the dye imageforming material is substantially nondiffusible subsequent to substantial dye image-forming material diffusion to the reception layer.

In accordance with the stated construction, the film unit design of the present invention specifically provides for the production of two separate and integral positive dye transfer images one of which is geometrically reversed with respect to the other such image. By this construction there is thus provided a film unit that will produce a positive right-reading diffusion transfer process dye image as a function of film unit photoexposure irrespective of whether or not a camera or exposure device is employed which possesses an optical reversed system. The construction thus allows for the employment of a single film unit type adapted for use in all existing reversal and nonreversal cameras presently distributed commercially for processing diffusion transfer-process color film units. It will be specifically noted that not only is the film units functional design inde pendent of the exposure device employed with respect to image reversal but that a single film unit cassette design may be employed with respect to accomplishing exposure of the film unit since each exposure is incident on the same surface of the film unit and each such exposure provides at least one right-reading positive dye image. Specifically, single surface exposure of the film unit in an exposure device possessing reversal optics provides a right-reading dye transfer image in the first reception layer viewed from the exposure surface of the film unit and a geometrically reversed dye transfer image in the second reception layer viewed from the opposite surface of the film unit, whereas exposure of the same surface of the film unit in. an exposure device which does not provide image reversal provides a rightreading dye transfer image in the second reception layer and a geometrically reversed dye image in the first reception layer. The advantages derived from the film units construction are readily apparent from the flexability of the film units design including uniform cassette and film design parameters and specifically encompasses the efficiencies and economics resultant from decreased raw materials inventories, manufacturing machine design uniformity and decreased capital investment and labor costs, simplified packaging considerations, and decreased product inventory, and distribution costs among others.

In view of the fact that the preferred dye imageforming materials comprises dyes which are silver halide developing agents, as stated above, for purposes of simplicity and clarity, the present invention will be fur ther described hereinafter in terms of such dyes, without limitation of the invention to the illustrative dyes denoted, and, in addition the photographic film unit structure will be detailed hereinafter employing the lastmentioned preferred structural. embodiment, without limitation of the invention to the preferred structure denoted.

The dye developers are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function" is meant a grouping adapted to develop exposed silver halide. A preferred silver halide developing function is a hy droquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the developing function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

The dye developers are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. The dye developers employed may be incorporated in the respective silver halide emulsion, in a preferred embodiment, or in a separate layer contiguous the respective silver halide stratum. Specifically, the dye developer may, for example, be in a coating or layer behind or directly disposed in the respective silver halide stratum and such dye developer structure may be applied by use of a coating solution containing about 0.5 to 8 percent, by weight, of the respective dye developer distributed in a film-forming natural, or synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the chosen diffusion transfer fluid processing composition.

An extensive compilation of specific dye developers particularly adapted for employment in photographic diffusion transfer processes is set forth in U.S. Pat. No. 2,983,606 and in the various copending U.S. applications referred to in that patent, especially in the table of U.S. applications incorporated by reference into the patent as detailed in column 27. As examples of additional U.S. patents detailing specific dye developers for photographic transfer process use, mention may be made of U.S. Pat. Nos. 2,983,605; 2,992,106;

3,141,722; 3,142,565; and the like.

The silver halide strata comprising the multicolor photosensitive laminate preferably possess predominant spectral sensitivity to separate regions of the spectrum and each has associated therewith a dye developer which is, most preferably, substantially soluble in the reduced form only at a first pH possessing, subsequent to processing, a spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion.

In a preferred embodiment of the present invention, the film unit is specifically adapted to provide for the production of a multicolor dye transfer image and the photosensitive laminate comprises, in order, at least two selectively sensitized silver halide emulsion strata each having dye image-providing material of predetermined image color subsequent to processing associated therewith which is soluble and diffusible substantially only at a first pH, as a function of the photoexposure of its associated silver halide emulsion stratum.

The silver halide emulsions comprising the multicolor photosensitive laminate preferably possess predominant spectral sensitivity to separate regions of the spectrum and each has associated therewith a dye, which is a silver halide developing agent and is, most preferably, substantially soluble in the reduced form only at a first pH, possessing subsequent to photoexposure or processing a spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion. Specifically preferred dyes comprise dyes which exhibit major spectral absorption outside of the primary regions of thd spectrum to which the associated silver halide emulsion is sensitive and a spectral transmission substantially complementary to that absorption, during exposure of the emulsion, and major spectral absorption within the spectral range to which the associated silver halide emulsion is sensitive and a spectral transmission substantially complementary to that absorption, subsequent to exposure or processing of said emulsion, for example, of the type disclosed in US. Pat. No. 3,307,947.

In one embodiment each of the emulsion strata, and its associated dye, may be spaced from the remaining emulsion strata, and their associated dye, by separate alkaline solution permeable polymeric interlayers and the dyeable polymeric layer next adjacent the polymeric acid layer may be separated from that layer by an alkaline solution permeable polymeric spacer layer, most preferably a polymeric spacer layer having de creasing permeability to alkaline solution with increasing temperature.

In such preferred embodiments of the invention, the silver halide emulsion comprises photosensitive silver halide dispersed in gelatin and is about 0.6 to 6 microns in thickness; the dye itself may be dispersed in an aqueous alkaline solution permeable polymeric binder, preferably gelatin, as a separate layer about 1 to 7 microns in thickness; the alkaline solution permeable polymeric interlayers, for example, gelatin, may be about 1 to microns in thickness; the alkaline solution permeable and dyeable polymeric layers are transparent and may be about 0.25 to 0.4 mil in thickness; the alkaline solution polymeric spacer layers are transparent and may be about 0.1 to 0.7 mil in thickness; the alkaline solution permeable polymeric acid layers are transparent and may be about 0.3 to 1.5 mils in thickness; and the dimensionally stable transparent layers are alkaline solution impermeable and may be about 2 to 6 mils in thickness. It will be specifically recognized that the relative dimensions recited above may be appropriately modified, in accordance with the desires of the operator, with respect to the specific product to be ultimately prepared.

In the preferred embodiment of the present inventions film unit for the production of a multicolor transfer image, the respective silver halide/dye developer units of the photosensitive element will be in the form of a tripack configuration which will ordinarily comprise a yellow dye developer/bluesensitive emulsion unit, a cyan dye developer/red-sensitive emulsion unit and a magenta dye developer/green-sensitive emulsion unit intermediate those units, recognizing that the relative order of such units may be varied in accordance with the desires of the operator.

In those instances, where either or both the respective yellow and magenta dye developers, employed in a preferred tripack configuration which positions the yellow dye developer/blue-sensitive emulsion unit distal the opaque layer dimensionally stable transparent layer and the cyan dye developer/red-sensitive emulsion unit proximal the opaque layer to provide the multicolor transfer image, comprise a dye developer which exhibits major spectral absorption outside of the primary region of the spectrum to which its associated silve halide emulsion is sensitive and a spectral transmission substantially complementary to that absorption, during exposure of the emulsion, then, in many circumstances, it may be advantageous to incorporate filter agents adapted to insure the correct selective exposure of the respective emulsions less proximal the exposure surface of the laminate. Specifically, in the instance where the yellow dye developer exhibits major spectral transmission within the primary regions of the spectrum to which its associated silver halide emulsion is sensitive, that is, the blue region of the visible spectrum, during exposure of the emulsions, then a yellow filter agent may advantageously be incorporated intermediate the blue-sensitive emulsion and the remaining greenand red-sensitive emulsions, in order to prevent undesired exposure of the latter emulsions by reason of their inherent sensitivity to actinic radiation within the blue range of the spectrum generally present. In the instance where the magenta dye developer employed exhibits major spectral transmission within the primary region of the spectrum to which its associated silver halide emulsion is sensitive, that is, the green region of the visible spectrum, during exposure of the emulsions, a magenta filter agent may be advantageously incorporated intermediate the greenand red-sensitive emulsions in instances wherein the red-sensitive emulsion possesses sensitivity to actinic radiation within the green region of the spectrum.

Reference is now made to FIGS. 1 through 7 of the drawings wherein there is illustrated a preferred film unit of the present invention and wherein like numbers, appearing in the various figures, refer to like components.

As illustrated in the drawings, FIG. 1 sets forth a perspective view of the film unit, designated 10, and each of FIGS. 2 through 7 illustrate diagrammatic crosssectional views of film unit 10, along the stated section lines 2-2, 3-3, 55 and 77, during the various depicted stages in the performance of a photographic diffusion transfer process as detailed hereinafter.

Film unit 10 comprises rupturable container 11, retaining, prior to processing, aqueous alkaline solution 12, and photosensitive element 13 including, in order, dimensionally stable transparent layer 24a; neutralizing layer 23a; spacer layer 22a; image-receiving layer 210; blue-sensitive silver halide emulsion layer 15 containing yellow dye developer; interlayer 16; green-sensitive silver halide emulsion layer 17 containing magenta dye developer; interlayer 18; red-sensitive silver halide emulsion layer 19 containing cyan dye developer; opaque layer 20; image-receiving layer 211); spacer layer 22b; neutralizing layer 23b; and dimensionally stable transparent layer 24b, both layer 24a and layer 2417 comprising an actinic radiation transparent and processing composition impermeable flexible sheet material.

Photosensitive element 13 may be provided with a binding member 26 extending around, for example, the specified edges of the element maintaining the element intact except at the interface between first imagereceptive layer 21a and blue-sensitive silver halide emulsion layer 15 during distribution of processing composition 12. As illustrated in the figures, the binding member may comprise a pressure-sensitive tape 26 securing the photosensitive elements components together at film unit 10s specified edges. Tape 26 will also act to maintain processing composition 12 intermediate first reception layer 21a/blue-sensitive silver halide emulsion layer 15 and upon application of compressive pressure to container 11 and distribution of its contents intermediate stated components 21a and 15. Under such circumstances, binder tape 26 will act to prevent leakage of processing composition from the film unit during and subsequent to photographic processing.

As illustrated, binding sheet 26 overlying and secured to the trailing edge sections of transparent layer 24a and transparent layer 2 11b cooperates with the trailing edge of each of the transparent layers to provide an enclosed chamber or trap area 2 adapted to secure and retain excess processing composition 12, employed to insure adequate processing composition coverage upon distribution. To further facilitate distribution of processing composition 12 between transparent layer 24a and transparent layer 24b, binding member 26 may be provided with one or more air release vents 1 associated with the trailing edge section of the film unit and preferably in direct communication with trap chamber 2 in order to facilitate release of air from the film unit during distribution of processing composition 12.

Rupturable container 11 may be of the type shown and described in any of US. Pat. Nos. 2,543,181; 2,634,886; 2,653,732; 2,723,051; 3,056,491; 3,056,492; 3,152,515; and the like. In general, such containers will comprise a rectangular blank of fluidand air-impervious sheet material folded longitudinally upon itself to form two walls 27 which are sealed to one another along their longitudinal and end margins to form a cavity in which processing solution 12 is retained. The longitudinal marginal seal 28 is made weaker than the end seals 29 so as to become unsealed in response to the hydraulic pressure generated within the fluid contents 12 of the container by the application of compressive pressure to walls 27 of the container.

As illustrated in FIGS. 1, 2 and 4, container 11 is fixedly positioned and extends transverse a leading edge of photosensitive laminate 13 whereby to effect unidirectional discharge of the containers contents 12 intermediate first reception layer 2121 and surface 32 of blue-sensitive silver halide emulsion layer 15, upon application of compressive force to container 11. Thus, container 11, as illustrated in FIG. 2, is fixedly positioned and extends transverse a leading edge of laminate 13 with its longitudinal marginal seal 28 directed toward the leading edge of surface 32. As shown in FIGS. 1, 2 and 4, container 11 is fixedly secured to laminate 13 by extension 30 of tape 26 extending over a portion of one wall 27 of the container, in combination with a separate retaining member such as illustrated retaining tape 31 extending over a a portion of the other wall 27 of the container and a portion of laminate l3s surface 32 generally equal in area to about that covered by tape 26.

As illustrated in FIGS. 1, 2 and 4, extension flap 30 of tape 26 may be of such area and dimensions that upon, for example, manual separation of container 11 and leader 31, subsequent to distribution of the composition, from the remainder of film unit 10, flap 30 may be folded over the edge of laminate 13, previously covered by leader 31, in order to facilitate maintenance of the laminates structural integrity, for example, during the flexations inevitable in storage and use of the processed film unit, and to provide a suitable mask or frame, for viewing of the transfer image through the picture viewing area of transparent layer 24. Preferably, however, the film unit will be maintained intact subsequent to processing including retention of the exhausted container, the processing composition in the spacial position assumed during processing. In such in stance, the processing composition employed should possess the requisite adhesive capacity, in both the fluid and dry states, to enhance the: integrity and stability of the spacial arrangement assumed.

In general, in a particularly preferred embodiment, the opacity of processing composition 12 when distributed will be sufficient to prevent further exposure of the film units silver halide emulsion or emulsions, by actinic radiation incident on transparent layer 24a during processing of the unit in the presence of radiation actinic to the emulsion or emulsions. Accordingly, the film unit may be processed, subsequent to exposure, in the presence of such radiation, in view of the fact that the silver halide emulsion or emulsions of the laminate are appropriately protected from incident radiation, at one major surface by the opaque layer or layers 21) and at the remaining major surface by opaque processing composition 12 as further described hereinafter. If the illustrated binder tapes are also opaque, as stated above, edge leakage of actinic radiation incident on the emulsion or emulsions will also be: prevented. The selected opaque processing composition and opaque layer or layers 211, however, should be one providing a background suitable for viewing the respective dye developer transfer images formed in the first and second dyeable polymeric layers. In general, while substantially any opaque processing composition and permeable opaque layer may be employed, it is preferred that a processing composition and layer be selected that will not interfere with the color integrity of the respective llll dye transfer images carried by the first and second reception layers, as viewed by the observer, and, most preferably, an opaque processing composition and opaque layer which is aesthetically pleasing to the viewer and does not provide a background noise signal degrading, or detracting from, the information content of the respective dye images. Particularly desirable opaque compositions will be those providing a white background, for viewing the respective transfer images, and specifically those adapted to be employed to provide background for reflection photographic prints and, especially, those layers possessing the optical properties desired for reflectance of incident radiation.

The opaque layer may comprise substantially any opacifying agent compatible with the photographic systern, such as, for example, barium sulfate, titanium dioxide, barium stearate, silver flake, zirconium oxide, and the like, which may be distributed in a permeable polymeric matrix or binder, such as, for example, gelatin, polyvinyl alcohol, and the like.

A particularly preferred opaque layer comprises titanium dioxide due to its highly effective reflection properties. In general, a coating composition, for example, hydroxyethylcellulose, containing sufficient titanium dioxide to provide a precent reflectance of about 85 to 90 percent, respectively, will be employed. In the most preferred embodiments, the percent reflectance de sired thus will be in the order of about 85 percent.

Where it is desired to increase the opacifying capacity of a layer containing, for example, titanium dioxide, beyond that ordinarily obtained, an additional opacifying agent such as carbon black, for example, in a concentration of about one part carbon black to 100 to 500 parts titanium dioxide may be provided to the layer. Preferably, however, such additional opacifying capacity will be provided by constituting the opacifying layer as a plurality of more or less discrete layers, the layer next adjacent the transparent support comprising A reflection layer and the succeeding layer or layers comprising one or more opacifying agents possessing greater opacifying capacity than that ordinarily obtained from the reflecting agent or agents employed.

Such additional opacifying agent may be any of the multiplicity of such agents known in the art such as carbon black, iron oxide, titanium (III) oxide, titanium (III) hydroxide, and the like. In preferance, the agent or agents should be selected which possess the maximum opacifying capacity per unit weight, is photographically nondeleterious and is substantially nondiffusible throughout the film unit subsequent to distribu- -tion. A particularly preferred agent has been found to comprise carbon black employed in a concentration effective, taken together with the selected reflecting agent, to provide the opacity required to prevent undesired physical fogging of the emulsion formulations selected and employed by radiation transmitted through the spread processing composition.

The fluid contents of the container preferably comprise an aqueous alkaline solution having a pH and sol vent concentration at which the dye developers are soluble and diffusible and contains inorganic lightreflecting pigment and at least one optical filter agent at a pH above the pKa of such agent in a quantity sufficient, upon distribution, effective to provide a layer exhibiting optical transmission density about six and optical reflection density about one to prevent exposure of photosensitive silver halide emulsion layers 15, 17 and 19 by actinic radiation incident on dimensionally stable transparent layer 240 during processing in the presence of such radiation and to afford immediate viewing of dye image formation in image-receiving layer 21a, in addition to image-receiving layer 21b, during and subsequent to dye transfer image formation. Accordingly, the film unit may be processed, subsequent to distribution of the composition, in the presence of such radiation, in view of the fact that the silver halide emulsion or emulsions of film unit 10 are appropriately protected by incident radiation, at one major surface of the opaque processing composition and at the remaining major surface by opaque layer 20. If the illustrated binder tapes are also opaque, edge leakage of actinic radiation incident on the emulsion or emulsions will also be prevented.

The selected reflecting pigment should be one providing a background suitable for viewing the dye developer transfer image formed in the dyeable polymeric layer 21a and, as previously mentioned, while substantially any reflecting agent may be employed, it is preferred that a reflecting agent be selected that will not interfere with the color integrity of the dye transfer image, as viewed by the observer, and, most preferably, an agent which is aesthetically pleasing to the viewer and does not provide a background noise signal degrading, or detracting from, the information content of the image.

As examples of reflecting pigments adapted for employment in processing composition 12, mention may be made of those specifically identified above.

A particularly preferred processing composition reflecting agent comprises titanium dioxide due to its highly effective reflection properties. In general, in such preferred processing composition embodiment, a processing composition containing about 40 to grams of titanium dioxide dispersed in 100 cc. of water will provide a percent reflectance of about to percent.

In embodiments wherein the dispersion comprises a preformed layer positioned intermediate the first reception layer and next adjacent silver halide layer, the pigment layer will be sufficiently transparent to allow transit of exposing radiation through the pigment layer and may comprise titanium dioxide reflecting agent possessing a particle size distribution averaging about 0.2 micron in diameter and preferably about 0.05 micron in diameter as initially present preceding exposure of the film unit, which preferred materials, upon contact with aqueous alkaline processing composition, preferably aggregate to provide particles possessing a diameter about 0.2 micron in diameter and will be coated at a coverage of about 200 to 1,000 mgs./ft Specifically, the reflecting agent will be present in a quantity insufficient to prevent exposure of the emulsion layers by actinic radiation incident on the dimensionally stable transparent layer of the film unit but in a concentration sufficient, subsequent to processing, to mask dye developer associated with the silver halide emulsion strata from the dye transfer image, and to mask processing composition residuum containing additional opacifying agent, e.g., 3 to 20 grams of carbon black or the like per cc. of processing composition, distributed intermediate the reflecting agent and the next adjacent silver halide emulsion unit in accordance with the preferred structure of this embodiment. In the preferred construction of such embodiment, the pigment such as titanium dioxide will be thus intially present in a relatively small particle size to provide efficient transit of radiation through the reflecting layer during exposure which, upon contact with an alkaline process ing composition and aggregation of the pigment particles, provides efficient light reflectivity and masking capacity subsequent of such aggregation.

In general, the opacifying adjuvants including the re flecting agents and optical filter agents to be employed are those which remain substantially immobile within their respective compositions during and subsequent to photographic processing and particularly those reflecting agents which comprise insoluble and nondiffusible inorganic pigment dispersions within the composition in which they are disposed.

Where desired, opacifying adjuvants accordingly may thus be distributed in whole or in part within a processing composition permeable polymeric matrix such as gelatin and/or any other such polymeric matrixes as are specifically denoted throughout the specification as suitable for employment as a matrix binder and may be distributed in one or more of the film unit layers which may be separated or contiguous, intermediate the im' age-receiving layer and next adjacent silver halide layer, provided that its distribution and concentration is effective to provide the denoted post processing masking function, and/or in whole or in part the reflecting agent may be ultimately disposed within the processing composition residuum located intermediate the image-receiving layer and next adjacent silver halide emulsion strata and associated dye image-forming material.

The optical filter agent selected should be one exhibiting, at a pH above its pKa, maximum spectral absorption of radiation at the wavelengths to which the film units photosensitive silver halide layer or layers are sensitive and should be substantially immobile or nondiffusible within the pigment dispersion, during performance of its radiation filtration function, in order to maintain and enhance the optical integrity of the dispersion as a radiation filter unit functioning in accordance with the present invention, and to prevent its diffusion into and localized concentration within an image-receiving layer thereby decreasing the efficiency of the reflecting pigment dispersion as a background against which image formation may be immediately viewed, during the initial stages in the diffusion transfer processing of the film unit, by filter agent absorption of dispersion reflected visible radiation prior to reduction in the environmental pH below the pKa of the agent. Commensurate with the spectral sensitivity range of the associated silver halide layer or layers, the optical filter agent selected may comprise one or more filter dyes possessing absorption complementary to such silver halide layers in order to provide effective protection against physical fog providing radiation during processing. Recognizing that the filter agent absorption will derogate from image-viewing characteristics by contaminating reflecting pigment background, the selected agents should be those exhibiting major spectral absorption at the pH at which processing is effected and minimal absorption at a pH below that which obtains during transfer image formation. Accordingly, the selected optical filter agent or agents should possess a pKa below that of the processing pH and above that of the environmental pH subsequent to transfer image formation, and will be preferably selected for employment in the minimum concentration necessary to provide an optical transmission density about six, at wavelengths at which the silver halide layer or layers are maximally responsive, and an optical reflection density about one at such wavelengths.

As specific examples of such pH-sensitive optical filter agents adapted for employment in the practice of the present invention, reference is directed to the agents set forth in aforementioned US. Pat. Nos. 3,647,437; 3,702,244; and 3,702,245, incorporated herein by reference.

It will be recognized that, where desired, the selected optical filter agent or agents may be initially disposed in or as a layer intermediate the first reception layer and next adjacent silver halide layer at a pH below the pKa of the selected agent or agents and may be converted to a radiation filtering species by contact of such agent with processing composition effecting appropriate modulation of the agents pKa. and preferably distributed intermediate the first reception layer and the optical filter agent layer and retaining reflecting pigment adapted to mask filter agent if not totally dis charged subsequent to processing of the film unit.

Optionally, the reflecting pigment opacifying agent may also be formed intermediate the first reception layer and next adjacent silver halide layer, during photographic processing of the film unit. Specifically, as

reflecting agent precursors adapted for employment mention may be made of ionizable, white, inorganic, visible light-reflecting pigment generating salts such as barium chloride, zirconium chloride, and the like, the cation of which upon contact with, for example, sulfate ions present in the selected processing composition and generally derived from ionizable salts such as sodium sulfate, etc., form reflecting agent pigment salts such as barium sulfate, zirconium sulfate, and the like; ionizable salts such as zinc sulfate and the like, the cation of which upon contact with the anion of ionized sodium or potassium hydroxide present in the selected processing composition form reflecting agent pigment such as zinc oxide and the like; ionizable salts such as zinc acetate and the like, the cation of which upon contact with sulfide ions present in the selected processing compositions and generally derived from ionizable salts such as sodium sulfide, etc., form reflecting agent such as zinc sulfide and the like; etc. It will be recognized that where desired the functional cation of the exemplary materials may optionally be disposed in the processing composition employed and the anion initially disposed in the processing composition permeable layer; that such adjuvants as are disclosed as initially disposed in the processing composition alternatively may be selectively disposed within the film unit insulated from functional generation of the reflecting agent preceding exposure of the film unit, for example, preceding processing composition solubilization of such adjuvant and/or required diffusion and contact between the reactants intermediate the image-receiving layer and next adjacent photosensitive silver halide emulsion layer; and that reflecting agent may be in part generated within the image-receiving and/or next adjacent silver halide emulsion strata of the film unit.

A particularly preferred embodiment employs a metathetical reaction between selected precursor salts, the respective exchange of cations or anions of which provide for the simultaneous generation of two separate reflecting agents such as, for example, the metathetical generation of both barium sulfate and zinc sulfide white, inorganic salt pigments by the in situ reaction of substantially colorless barium sulfide and zinc sulfate precursor salts. Such preferred embodiments provide for the in-process generation of an increased quantity of reflecting agent per unit volume of precursor salts employed.

A particularly preferred reflecting agent comprises barium sulfate due to its highly effective reflection properties.

In general, in the preferred embodiments, the reflecting agent precursor selected will, as previously denoted, comprise a precursor specifically adapted to provide a substantially white inorganic pigment which reflects visible light and, in particularly preferred embodiments, will be coated at a coverage effective to provide 200 to 1,000 mgs./ft. reflecting agent, as a result of processing, which coverage is generally sufficient, subsequent to processing, to mask opacifying agent distributed in the processing composition and any residual dye developer present intermediate the image-receiving layer and the next adjacent silver halide layer.

A particularly preferred processing composition opacifying agent to be employed in combination with preformed and/or in situ formed reflecting pigment systems has been found to comprise carbon black due to its highly efficient absorption characteristics. In general, a processing composition particularly desired for employment in the practice of the present invention will contain carbon black in a concentration effective, e.g., about 3 to 20 grams of carbon black dispersed in 100 cc. of water, to prevent transmission, through the distributed stratum comprising the composition, of in excess of 95 percent of the actinic radiation incident on the stratum.

In the performance of a diffusion transfer multicolor process employing film unit 10, the unit is exposed to radiation, actinic to photosensitive laminate 13, incident on the laminates exposure surface 34, as illustrated by FIG. 2.

Subsequent to exposure, as illustrated by FIGS. 2 and 4, film unit is processed by being passed through opposed suitable gapped rolls 33 in order to apply compressive pressure to frangible container 11 and to effect rupture of longitudinal seal 28 and distribution of processing composition 12, containing opacifying agent and having a pH at which the cyan, magenta and yellow dye developers are soluble and diffusible, intermediate first image-receiving layer 21a and blue-sensitive silver halide emulsion layer 15 on a coextensive surface 32.

Processing composition 12 permeates emulsion layers l5, l7 and 19 to initiate development of the latent images contained in the respective emulsions. The cyan, magenta and yellow dye developers, of layers 15, 17 and 19, are immobilized, as a function of the development of their respective associated silver halide emulsions, preferably substantially as a result of their conversion from the reduced form to their relatively insoluble and nondiffusible oxidized form, thereby providing imagewise distributions of mobile, soluble and diffusible cyan, magenta and yellow dye developer, as a function of the point-to-point degree of their associated emulsions exposure. At least part of the imagewise distributions of mobile cyan, magenta and yellow dye developer transfer, by diffusion, to processing composition permeable polymeric layers 2la and 21b to provide to each layer a separate reception multicolor dye transfer image geometrically reversed with respect to each other. Subsequent to substantial transfer image formation, a sufficient portion of the ions comprising aqueous composition 12 transfer, by diffusion, through permeable polymeric reception layers 21a and 21b, permeable spacer layers 22a and 22b and to permeable polymeric acid layers 23a and 23b whereby solution 12 decreases in pH, as a function of neutralization, to a pH at which the cyan, magenta and yellow dye developers, in the reduced form, are substantially insoluble and nondiffusible, to provide thereby a separate laterally reversed multicolor dye transfer image viewable through dimensionally stable transparent layers 24a and 24b, respectively.

Subsequent to distribution of processing solution 12, container 11, optionally, may be manually dissociated from the remainder of the film unit, as described above.

As previously stated, the respective multicolor dye transfer image is viewable through dimensionally stable transparent layers 24a and 24b both during and subsequent to transfer image formation, in the preferred embodiment detailed above.

The present invention will be further illustrated and detailed in conjunction with the following illustrative constructions which set out representative embodiments and photographic utilization of the novel photographic film units of this invention, which, however, are not limited to the details therein set forth and are intended to be illustrative only.

Film units similar to that shown in the drawings may be prepared, for example, by coating, in succession, on a first 5 mil transparent polyester film base, the following layers:

1. the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high viscosity poly-(ethylene/maleic anhydride), 140 grams of n-butyl alcohol and 1 cc. of percent phosphoric acid to provide a polymeric acid layer at a coverage of about 2,500 mgs./ft.

2. a timing layer containing about a 40:1 ratio of a 60/30/4/6 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid and polyacrylamide at a coverage of about 500 mgs/ftf"; and

3. a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of about 400 mgs./ft. to provide a polymeric image-receiving layer;

4. a layer comprising a dispersion of TiO in gelatin at a coverage of about 1,500 mgs./ft. TiO and about mgs./ft. of polyacrylamide;

5. a layer comprising a dispersion of carbon black in gelatin at a coverage of about 300 mgs./ft. carbon black and about 50 mgs./ft. of gelatin;

6. a red-sensitive gelatino-silver iodobromide emulsion containing a solid dispersion of the cyan dye developer no onr-on,

coated at a coverage of about 80 mgs./ft. of silver, about 80 mgs./ft. dye developer and about 40 mgslft. of gelatin;

9. a layer of butyl acrylate/diacetone acryalmide/styrene/methacrylic acid (60/30/4/6) and polyacrylamide coated in a ratio of about 29:4, respectively, at a coverage of about 100 mgs./ft.

10. a blue-sensitive gelatino-silver iodobromide emulsion containing a solid dispersion of the yellow dye developer coated at a coverage of about mgs./ft. of silver, about mgslft. dye developer and about 100 mgs/ft. of gelatin; and

l 1. a layer of gelatin containing 4-methyl phenyl hydroquinone coated at a coverage of about 15 mgs/ft. hydroquinone and about 45 mgs./ft. of gelatin.

On a second 5 mil transparent polyester film base may be coated, in order, Layers l, 2 and 3 above.

The two components thus prepared may then be taped together in laminate form, at: their respective lateral and trailing edges, by means of a pressure-sensitive binding tape extending around, in contact with, and over the edges of the resultant laminate.

A rupturable container comprising an outer layer of lead foil and an inner liner or layer of polyvinyl chloride retaining an aqueous alkaline processing solution such as, for example, the processing compositions specifically detailed in copending US. application Ser. No. 246,669, filed Apr. 24, 1972, and which compositions may include, per 100 cc. of water, about 4.7 grams of potassium hydroxide, about 0.8 gram of carboxymethyl cellulose, about 42 grams of titanium dioxide, about 1.3 grams of N-benzyl-a-picolinium bromide, about 0.7 gram of N-phenethyl-a-picolinium bromide, about 2 grams of an aqueous silica dispersion comprising about 30 percent SiO and one or more antifoggants such as about 0.6 gram of benzotriazole and about 0.03 gram of 6-methyl-5-bromo-4-azabenzimidazole, together with such other processing composition adjuvants, for example, those adjuvants specifically identified in the last-cited application, as the operator shall optionally select, may then be fixedly mounted on the leading edge of each of the laminates, by pressure-sensitive tapes interconnecting the respective containers and laminates, such that, upon application of compressive pressure to the container, its contents may be distributed, upon rupture of the containers marginal seal, between second polymeric image-receiving Layer 3 and its next adjacent gelatin Layer 111.

The photosensitive composite film units may be exposed through radiation incident on the transparent polyester film base and processed by passage of the exposed film units through appropriate pressure-applying members, such as suitably gapped, opposed rolls, to effect rupture of the container and distribution of its contents. Subsequent to processing, multicolor dye transfer image formation may be viewed through each transparent polyester layer against a titanium dioxide reflection layer.

Film units, fabricated essentially as denoted above, may be processed in the stated manner, at processing temperatures of from about 100 to 40 F., and may be exposed to a conventional step wedge to provide graphic illustration of the characteristic curves of the respective dye transfer images forming the multicolor dye positive images. Specifically, the detailed characteristic curves may be determined by plotting the density of the respective images to red, green and blue light, as a function of the log exposure of the photosensitive element, e.g., the characteristic cyan, magenta and yellow transfer image dye curves (read to red, green and blue reflected light) of the test and control film units.

By addition of an effective concentration of (])H 11 GOOH COOH K/ OClxHzrn and to the processing composition, image formation in the second image-receiving layer may be immediately viewed upon distribution of the processing composition by reason of the protection against incident radiation afforded the photosensitive silver halide emulsion layers by the composition s optical transmission density of about six density units and against the titanium dioxides effective reflective background afforded by reason of the composition possessing an optical reflection density of about one density units.

The pH and solvent concentration of the alkaline processing solution initially employed will preferably possess a pH above the pKa of the optical filter agents where the latter are employed, that is, the pH at which about 50 percent of the agents are present as the lesser absorbing species and about 50 percent are present as the greater absorbing species, preferably a pKa of about I l and most preferably about 12 and a pH at which the dye developers employed are soluble and diffusible. Although it has been found that the specific pH to be employed may be readily determined empirically for any dye developer and optical filter agent, or group of dye developers and filter agents, most particularly desirable dye developers are soluble at pH's above 9 and relatively insoluble at pI-Is below 9, in reduced form, and the system can be readily balanced accordingly for such dye developers. In addition, although as previously noted, the processing composition, in the preferred embodiment, will include the stated filmforming viscosity-increasing agent, or agents, to facilitate spreading of the composition and to provide maintenance of the spread composition as a structurally stable layer of the laminate, subsequent to distribution, it is not necessary that such agent be employed as a component of the composition. In the latter instance, however, it will be preferred that the concentration of solvent, that is, water, etc., comprising the composition be the minimum amount necessary to conduct the desired transfer process, in order not to adversely effect the structural integrity of the laminate and that the layers forming the laminate can readily accommodate and dissipate the solvent throughout during processing and drying without effecting undesirable dimensional changes in the layers forming the laminate.

As disclosed in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example, diethylamine, sodium hydroxide or sodium carbonate and the like, and preferably possessing a pH in excess of 12, and most preferably includes a vicsocity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular weight polymers such as polymeric, water-soluble ethers which are insert to a alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose. Additionally, film-forming materials or thickening agents whose ability to increase viscosity substantially unaffected if left in solution for a long period of time are also disclosed to be capable of utilization. As stated, the filmforming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of I00 cps. at a temperature of approximately 24 C. and preferably in the order of 100,000 cps. to 200,000 cps. at that temperature.

Neutralizing means, for example, a polymeric acid layer of the type discussed above will be incorporated, as stated, in the film unit of the present invention, to provide reduction of the alkalinity of the processing solution from a pH at which the dyes are soluble as a function of film unit photoexposure and above the pKa of selected optical filter agents where desired to a pH below the pKa of the filter agent selected and at which the dyes are substantially nondiffusible, in order to advantageously further stabilize and optimize reflectivity of the respective dye transfer images. In such instance, the neutralizing layer may comprise particulate acid reacting reagent disposed within the film unit or a polymeric acid layer, for example, a polymeric acid layer approximately 0.3 to 1.5 mils in thickness, positioned intermediate the first and/or second transparent support and the next adjacent image-receiving layer and the film unit may also contain a polymeric spacer or barrier layer, for example, approximately 0.1 to 0.7 mil in thickness, next adjacent the respective polymeric acid layer or layers, opposite the respective support layer, as previously described.

Specifically, the film units may employ the presence of a polymeric acid layer such as, for example, of the type set forth in U.S. Pat. No. 3,362,819 which, most preferably, includes the presence of an inert timing or spacer layer intermediate the polymeric acid layer carried on a support and the image-receiving layer.

As previously noted, the pH of the processing composition preferably is of the order of about least 12 to 14 and the pKa of the selected optical filter agents will accordingly preferably be in the order of 12 or greater. The polymer layer is disclosed to contain at least sufficient acid groups to effect a reduction in the pH of the image layer from a pH of about 12 to 14 to a pH of at least ll or lower at the end of the imbibition period, and preferably to a pH of about to 8 within a short time after imbibition, thus requiring, of course, that the action of the polymeric acid be accurately so controlled as not to interfere with either development of the negative or image transfer of unoxidized dye developers. For this reason, the pH of the image layer must be kept at a functional transfer level, for example, 12 to 14 until the dye image has been formed after which the pH is reduced very rapidly to a pH below that at which dye transfer may be accomplished, for example, at least about 1 l and preferably about pH 9 to 10. Unoxidized dye developers containing hydroquinonyl developing radicals diffuse from the negative to the posi' tive as the sodium or other alkali salt. The diffusion rate of such dye image-forming components thus is at least partly a function of the alkali concentration, and itis necessary that the pH of the image layer remain on the order of, for example, 12 to 14 until transfer of the necessary quantity of dye has been accomplished. The subsequent pH reduction, in addition to its desirable effect upon image light stability, serves a highly valuable photographic function by substantially terminating further dye transfer.

In order to prevent premature pH reduction during transfer processing, as evidenced, for example, by an undesired reduction in positive image density, the acid groups are disclosed to be so distributed in the polymer layer that the rate of their availability to the alkali is controllable, e.g., as a function of the rate of swelling of the polymer layer which rate in turn has a direct relationship to the diffusion rate of the alkali ions. The desired availability of the acid groups in the polymer layer may be effected by mixing acid polymer with a polymer free of acid groups, or lower in concentration of acid groups, and compatible therewith, as a modulated system, or by using only an acid polymer but selecting one having a predetermined acid group availability rate.

The layer containing the polymeric acid may also contain a water-insoluble polymer, preferably a cellulose ester, which acts to control or modulate the rate at which the alkali salt of the polymer acid is formed. As examples of cellulose esters contemplated for use, mention is made of cellulose acetate, cellulose acetate butyrate, etc. The particular polymers and combinations of polymers employed in any given embodiment are, of course, selected so as to have adequate wet and dry strength and when necessary or desirable, suitable subcoats are employed to help the various polymeric layers adhere to each other during storage and use.

The inert spacer layer of the last-mentioned patent, for example, an inert spacer layer comprising polyvinyl alcohol or gelatin, acts to time control the pH reduction by the polymeric acid layer. This timing is disclosed to be a function of the rate at which the alkali diffuses through the inert spacer layer. It is there stated to have been found that the pH does not drop until the alkalihas passed through the spacer layer, i.e., the pH is not reduced to any significant extent by the mere diffusion into the interlayer, but the pH drops quite rapidly once the alkali diffuses through the spacer layer.

As disclosed in aforementioned US. Pat. No. 3,362,819, the presence of an inert spacer layer was found to be effective in evening out the various reaction rates over a wide range of temperatures, for example, by preventing premature pH reduction when imbibition is effected at temperatures above room temperature, for example, at to F. By providing an inert spacer layer, that application discloses that the rate at which alkali is available for capture in the polymeric acid layer becomes a function of the alkali diffusion rates.

However, as disclosed in US. Pat. No. 3,455,686, preferably the aforementioned rate at which the cations of the alkaline processing composition, i.e., alkali ions, are available for capture in the polymeric acid layer should be decreased with increasing transfer processing temperatures in order to provide diffusion transfer color processes relatively independent of positive transfer image variations over an extended range of ambient temperatures.

Specifically, it is there stated to have been found that the diffusion rate of alkali through a permeable inert' polymeric spacer layer increases with increased processing temperature to the extent, for example, that at relatively high transfer processing temperatures, that is, transfer processing temperatures above approximately 80 F., a premature decrease in the pH of the transfer processing composition occurs due, at least in part, to the rapid diffusion of alkali from the dye transfer environment and its subsequent neutralization upon contact with the polymeric acid layer. This was stated to be especially true of alkali traversing an inert spacer layer possessing permeability to alkali optimized to be effective with the temperature range of optimum transfer processing. Conversely, at temperatures below the optimum transfer processing range, for example, temperatures below approximately 40 F., the lastmentioned inert spacer layer was disclosed to provide an effective diffusion barrier timewise preventing effective traverse of the inert spacer layer by alkali having temperature depressed diffusion rates and to result in maintenance of the transfer processing environments high pH for such an extended time interval as to facilitate formation of transfer image stain and its resultant degradation of the positive transfer images color definition.

It is further stated in the last-mentioned US. Pat. No. 3,455,686 to have been found, however, that if the inert spacer layer of the print-receiving element is replaced by a spacer layer which comprises a permeable polymeric layer exhibiting permeability inversely dependent on temperature, that is, a polymeric filmforming material which exhibits decreasing permeability to solubilized alkali derived cations such as alkali metal quaternary ammonium ions under conditons of increasing temperature, that the positive transfer image defects resultant from the aforementioned overextended pH maintenance and/or premature pH reduction are obviated.

As examples of materials, for use as the imagereceiving layer, mention may be made of solution dyeable polymers such as nylon as, for example, N- methoxymethyl polyhexamethylene adipamide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with filler as, for example, one-half cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4- vinylpyridine, as disclosed in U.S. Pat. No. 3,148,061, issued Sept. 8, 1964.

It will be noted that the liquid processing composition employed may contain an auxiliary or accelerating developing agent, such as p-methylaminophenol, 2,4- diaminophenol, p-benzylaminophenyl, hydroquinone, toluhydroquinone, phenylhydroquinone, 4-methylphenylhydroquinone, etc. It is also contemplated to employ a plurality of auxiliary or accelerating developing agents, such as a 3-pyrazolidone developing agent and a benzenoid developing agent, as disclosed in U.S. Pat. No. 3,039,869, issued June 19, 1962. As examples of suitable combinations of auxiliary developing agents, mention may be made of 1-phenyl-3-pyrazolidone in combination with p-benzylaminophenol and l-phenyl- 3-pyrazolidone in combination with 2,5-bisethylenimino-hydroquinone. Such auxiliary developing agents may be employed in the liquid processing composition or they may be initially incorporated, at least in part, in any one or more of the silver halide emulsion strata, the strata containing the dye developers, the interlayers, the image-receiving layer, or in any other auxiliary layer, or layers, of the film unit.

It may be noted that at least a portion of the dye developer oxidized during development may be oxidized and immobilized as a result of a reaction, e.g., an energy-transfer reaction, with the oxidation product of an oxidized auxiliary developing agent, the latter developing agent being oxidized by the development of exposed silver halide. Such a reaction of oxidized developing agent with unoxidized dye developer would regenerate the auxiliary developing agent for further reaction with the exposed silver halide.

In addition, development may be effected in the presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the processes disclosed in U.S. Pat. No. 3,173,786, issued Mar. 16, 1965.

It will be apparent that the relative proportions of the agents of the diffusion transfer processing composition may be altered to suit the requirements of the operator. Thus, it is within the scope of this invention to modify the herein described developing compositions by the substitution of preservatives, alkalies, etc., other than those specifically mentioned, provided that the pH of the composition is initially at the first pH required. When desirable, it is also contemplated to include, in the developing composition, components such as restrainers, accelerators, etc. Similarly, the concentration of various components may be varied over a wide range and when desirable adaptable components may be disposed in the photosensitive element, prior to exposure, in a separate permeable layer of the photosensitive element and/or in the photosensitive emulsion.

The dimensionally stable layers or sheets referred to may comprise any of various types of conventional transparent rigid or flexible materials, for example, pa-

pers and polymeric films of both synthetic types and those derived from naturally occurring products. Suitable materials include alkaline solution impermeable materials such as polymethacrylic acid methyl and ethyl esters; vinyl chloride polymers, polyvinyl acetal; polyamides such as nylon; polyesters such as polymeric films derived from ethylene glycol and terephthalic acid; and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetatepropionate or actate-butyrate. It will be recognized that one or more or the designated layers may not be required where the remaining layers of the laminate are such as to provide the functions of these layers in the absence of same, for example, where the remaining layers of the laminate provide the requisite dimensional stability and radiation filtering properties.

In all examples of this specification, percentages of components are given by weight unless otherwise indicated.

Although the invention has been discussed in detail throughout employing dye developers, the preferred image-providing materials, it will be readily recognized that other, less preferred, diffusion transfer process dye image-providing materials may be substituted in replacement of the preferred dye developers in the practice of the invention. For example, there may be employed dye image-forming materials such as those disclosed in U.S. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 3,148,062; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294; 3,330,655; 3,347,671; 3,352,672; 3,364,022; 3,443,939; 3,443,940; 3,443,941;

3,443,943; etc., wherein color diffusion transfer processes are described which employ color coupling techniques comprising, at least in part, reacting one or more dye image-providing color developing agents and one or more dye image-providing color formers or couplers to provide a dye transfer image to a superposed image-receiving layer and those disclosed in U.S. Pat. Nos. 2,774,668 and 3,087,817, wherein color diffusion transfer processes are described which employ the imagewise differential transfer of complete dyes by the mechanisms therein described to provide a transfer dye image to a contiguous image-receiving layer, and thus including the employment of dye image-providing materials in whole or in part initially insoluble or nondiffusible as disposed in the film unit which diffuse during processing as a direct or indirect function of exposure.

Where desired, the film unit may also contain ultraviolet absorbing materials to protect the mordanted dye transfer image from fading due to ultraviolet light such as those selected from the general class of benzotriazoles and benzophenones as, for example, the substituted Z-phenyI-benzotriazole agents disclosed in U.S.

Pat. Nos. 3,004,896; 3,189,615; etc.; the 2- hydroxybenzophenones such as 2-hydroxy-4- methoxybenzophenone; 2,2-dihydroxy-4- methoxybenzophenone; 2-hydroxy-4- octyloxybenzophenone; etc., both water and organic solvent soluble agents being contemplated, and/or brightening agents such as those selected from the general class of triazinestilbenes, coumarins, anthracenes, terphenyls, tetraphenylbutadienes, quinoxalines, conventional for use as fluorescent agents and as optical brightening agents. Suitable triazinestilbene optical brightening agents are disclosed in U.S. Pat. No.

2,933,390; coumarines are disclosed in British Pat. No. 786,234; and various agents are disclosed in US. Pat. Nos. 2,171,427; 2,473,475; 2,595,030; 3,660,578; and British Pat. Nos. 595,065; 623,849; 624,051; 624,052; 678,291; 681,642; 705,406; etc. Commercially available brightening agents are distributed under the trade designation Tinopal (SP, WR, SFG, BV277, 2B, GS, NG) Leucophor B, Calcoflour White MR, Blaneofor SC, Hitamine (BSP, N, SOL., 6T6), and the like, and commerically available ultraviolet absorbing agents are distributed under the trade designation Tinuvin and the like.

In general, ultraviolet absorbing and optical brightening agents may be employed in concentrations varying over an extended range. Suitable concentrations include those within the range of about 0.2 to mgs./ft. of receptor layer surface area and, preferably, between about 1 to 5 mgs./f t.

The agents may be incorporated in any one or more of the layers of the film unit preferably intermediate an opaque layer forming the background against which an image is viewed and the viewing surface in any suitable manner as, for example, a constituent component of the casting and/or coating solution or formulation employed to provide such layer or layers employing an organic solvent or water carrier or as a latex dispersion.

In the circumstances wherein the receptor layer or layers possess the dimensional stability to provide a self-sustaining layer conformation, the layer may optionally be coated on or carried by an appropriate dimensionally stable support layer of the various types and classes specifically designated hereinbefore or not at the election of the operator.

Ordinarily, when the image receptor stratum comprises a layer carried on a separate dimensionally stable support layer, the receptor stratum will comprise in the order of about 0.1 to 0.4 mil in thickness whereas such stratum employed as a self-sustaining layer will comprise in the order of about 3 to 6 mils in thickness.

In addition to conventional techniques for the direct dispersion of a particulate solid material in a polymeric, or colloidal, matrix such as ball-milling and the like techniques, the preparation of the dye developer and color coupler dispersions may also be obtained by dissolving the dye and/or coupler in an appropriate solvent, or mixture of solvents, and the resultant solution distributed in the polymeric binder, with optional subsequent removal of the solvent, or solvents, employed, as, for example, by vaporization where the selected solvent, or solvents, possesses a sufficiently low boiling point or washing where the selected solvent, or solvents, possesses a sufficiently high differential solubility in the wash medium, for example, water, when mea sured against the solubility of the remaining composition components, and/or obtained by dissolving both the polymeric binder and dye in a common solvent.

For further detailed treatment of solvent distribution systems of the types referred to above, and for an extensive compilation of the conventional solvents traditionally employed in the art to effect distribution of photographic color-providing materials in polymeric binders, specifically for the formation of component layers of photographic film units, reference may be made to US. Pat. Nos. 2,269,158; 2,322,027; 2,304,939; 2,304,940; 2,801,171; and the like.

For the production of the photosensitive gelatino silver halide emulsions employed to provide the film unit, the silver halide crystals may be prepared by reacting a water-soluble silver salt, such as silver nitrate, with at least one water-soluble halide, such as ammonium, potassium or sodium bromide, preferably together with a corresponding iodide, in an aqueous solution of a peptizing agent such as a colloidal gelatin solution; digesting the dispersion at an elevated temperature, to pro vide increased crystal growth; washing the resultant water-soluble salts by chilling the dispersion, noodling the set dispersion, and washing the noodles with cold water, or alternatively, employing; any of the various flocc systems, or procedures, adapted to effect removal of undesired components, for example, the procedures described in US. Pat. Nos. 2,614,928; 2,614,929; 2,728,662; and the like; after-ripening the dispersion at an elevated temperature in combination with the addition of gelatin and various adjuncts, for example, chemical sensitizing agents of US. Pat. Nos. 1,574,944; 1,623,499; 2,410,689; 2,597,856; 2,597,915; 2,487,850; 2,518,698; 2,521,926; and the like; all according to the traditional procedures of the art, as described in Neblette, C. B., Photography Its Materials and Processes, 6th Ed., 1962.

Optical sensitization of the emulsions silver halide crystals may be accomplished by contact of the emulsion composition with an effective concentration of the selected optical sensitizing dyes dissolved in an appropriate dispersing solvent such as methanol, ethanol, acetone, water, and the like; all according to the traditional procedures of the art, as described in Hammer, F. M., The Cyanine Dyes and Related Compounds.

Additional optional additives, such as coating aids, hardeners, viscosity-increasing agents, stabilizers, preservatives, and the like, for example, those set forth hereinafter, also may be incorporated in the emulsion formulation, according to the conventional procedures known in the photographic emulsion manufacturing art.

The photoresponsive material of the photographic emulsion will, as previously described, preferably comprise a crystal of silver, for example, one or more of the silver halides such as silver chloride, silver iodide, silver bromide, or mixed silver halides such as silver chlorobromide, silver chloriodobromide: or silver iodobromide, of varying halide ratios and varying silver concentrations.

As the binder for the respective emulsion strata, the aforementioned gelatin may be, in whole or in part, replaced with some other colloidal material such as albumin; casein; or zein; or resins such as a cellulose derivative, as described in U.S. Pat. Nos. 2,322,085 and 2,327,808; polyacrylamides, as described in US. Pat. No. 2,541,474; and vinyl polymers such as described in an extensive multiplicity of readily available US. and foreign patents.

Although the preceding description of the invention has been couched in terms of the preferred photosensitive component construction wherein at least two selectively sensitized photosensitive strata are in contiguous coplanar relationship and, specifically, in terms of the preferred tripack type structure comprising a redsensitive silver halide emulsion stratum, a greensensitive silver halide emulsion stratum and a bluesensitive silver halide emulsion stratum having associated therewith, respectively, a cyan dye developer, a

magenta dye developer and a yellow dye developer, the photosensitive component of the film unit may comprise at least two sets of selectively sensitized minute photosensitive elements arranged in the form of a photosensitive screen wherein each of the minute photosensitive elements has associated therewith, for example, an appropriate dye image-forming material in or behind its respective silver halide emulsion portion. In general, a suitable photosensitive screen may comprise minute red-sensitized emulsion elements, a minute green-sensitized emulsion elements and minute bluesensitized emulsion elements arranged in side-by-side relationship in a screen pattern and having associated therewith, respectively, for example, a cyan, a magenta and a yellow dye developer.

The present invention also includes the employment of a black dye image-providing material and the use of a mixture of, for example, dye developers adapted to provide a black-and-white transfer image, for example, the employment of dye developers of the three subtractive colors in an appropriate mixture in which the quantities of the dye developers are proportioned such that the colors combine to provide black.

Where in the specification, the expression positive image has been used, this expression should not be interpreted in a restrictive sense since it is used primarily for purposes of illustration, in that it defines the image produced on the image-carrying layers as being reversed, in the positive-negative sense, with respect to the image in the photosensitive emulsion layers. As an example of an alternative meaning for positive image, assume that the photosensitive element is exposed to actinic light through a negative transparency. In this case, the latent image in the photosensitive emulsion layers will be a positive and the dye image produced on the image-carrying layers will be negative. The expression positive image is intended to cover such an image produced on the image-carrying layer.

In addition to the described essential layers, it will be recognized that the film unit may also contain one or more subcoats or layers, which, in turn, may contain one or more additives such as plasticizers, intermediate essential layers for the purpose, for example, of improving adhesion, and that any one or more of the described layers may comprise a composite of two or more strata of the same, or different, components and which may be contiguous, or separated from, each other, for example, two or more neutralizing layers or the like.

In accordance with the present invention, the preferred form of the film assemblage for the production of a dye reflection print comprises a photosensitive film unit constructed as described above and specifically adapted to be processed in the presence of ambient radiation and the dye reflection print image to be viewed during and subsequent to processing without separation of film unit components and includes leader means for coupling film units and selectively withdrawing the units sequentially from a film pack or magazine and opacifying agent, preferably disposed in whole or in part in the processing composition, taken together with the opaque layer, adapted to prevent exposure of the first sheet elements photoresponsive material by radiation actinic thereto incident on the film unit in the processing mode.

A preferred form of film pack or magazine embodying the designated film units comprises a plurality of the film assemblies, each adapted to be individually exposed in a camera, enclosed in an initially light-proof container which allows the film units to be sequentially exposed. The container includes a forward wall having a light-transmitting section, e.g., an exposure aperture, therein and an opening in one wall through which film assemblies can be individually withdrawn. The photosensitive film units are positioned together in stacked relationship within the container underlying the exposure aperture with the exposure surface of each film unit uppermost and the rupturable container positioned adjacent the opening through which the film units are withdrawn so that following the exposure of each film unit, the unit is moved, by drawing on the leader of the film unit, and withdrawn from the container through the opening. The film pack is initially provided with a cover element or sheet mounted within the container and extending across the exposure aperture for closing the aperture against the admission of light. The cover element also includes a leader extending from the container through the opening and being removable therethrough.

The film pack is employed by being positioned in a camera, including a pair of juxtaposed pressureapplying members, with the opening located adjacent the pressure-applying members and the exposure aperture disposed approximately in the exposure plane of the camera. A leader for the cover element extends from the pack and from the camera where the last mentioned leader may be grasped for withdrawing the cover element from the pack through the pressureapplying members and camera to allow the film units of the pack to be selectively exposed. After each successive film unit is exposed, that film unit is then individually withdrawn from the container and camera between the pressure-applying members by withdrawing the leader of the first film unit and of successive film units from the container and camera.

Reference is now made to FIGS. 1, 8 and 9 of the drawings wherein there are illustrated film units and an assemblage of film units in the form of a film pack. Each film unit 10 includes a leader sheet 31 having a leading end section designated 38 and a trailing end section 40 at which the leader sheet 31 is coupled with the film unit near the leading end thereof. Leader sheet 31 including leading and trailing end sections 38 and 40 is approximately equal in width to the film unit 10 and leading end section 38 of each leader sheet 31 is secured to the trailing end of the next preceding film unit or, in the case of the first film unit, to the cover sheet, preferably near the trailing end section of the preceding element (cover sheet or film unit). The length of leader sheet 31 between its leading edge attachment to one film unit and the trailing edge to the next succeeding film unit is substantially equal to the length of the film units between their leading and trailing edges; and the connected film units and leaders are arranged in zig-zag folded relation.

A film pack or assemblage of film units 10 embodying the invention is shown in FIGS. 8 and 9 of the drawings. This film pack, designated 44, comprises all of the components and structure including pressure-applying means required to produce a plurality of diffusion transfer process color prints. Film pack 44 comprises a generally parallelepiped-shaped container or box 46 

2. A composite photographic diffusion transfer color process film unit as defined in claim 1 wherein said processing composition possesses a first processing pH and said film unit includes means for converting, subsequent to substantial dye transfer image formation in each of said first and said second dyeable layers, said processing composition from said first processing pH to a second pH at which each of said dye transfer images exhibit increased stability.
 3. A composite photographic diffusion transfer process film unit as defined in claim 2 wherein said first processing pH is an alkaline pH and said second pH is lower than said first pH.
 4. A composite photographic diffusion transfer process film unit as defined in claim 3 wherein said second pH is > one pH unit less than said first pH.
 5. A composite photographic diffusion transfer process film unit as defined in claim 2 wherein said means for converting said processing composition from said first to said second pH subsequent to substantial dye transfer image formation in each of said first and said second dyeable layers comprise a polymeric neutralizing layer positioned intermediate at least one of said first dimensionally stable transparent layer and said first dyeable layer, and said second dimensionally stable transparent layer and said second dyeable layer.
 6. A composite photographic diffusion transfer process film unit as defined in claim 1 wherein said opacifying agent is present in a quantity effective, upon distribution intermediate said second dyeable layer and the photosensitive silver halide layer next adjacent, to prevent exposure of said photosensitive silver halide layer during processing of said film unit in the presence of radiation actinic to said photosensitive layer and incident on said second dimensionally stable transparent layer and said opaque layer is effective to prevent exposure of said photosensitive layer during processing of said film unit in the presence of radiation actinic to said photosensitive layer and incident on said first dimensionally stable layer.
 7. A composite photographic diffusion transfer process film unit as defined in claim 1 wherein said opaque layer is actinic radiation reflective.
 8. A composite photographic diffusion transfer process film unit as defined in claim 7 wherein said opaque layer comprises titanium dioxidE dispersed in a processing composition permeable polymeric binder.
 9. A composite photographic diffusion transfer process film unit as defined in claim 8 wherein said opaque layer comprises a composite including a layer containing carbon black dispersed in a processing composition permeable polymeric binder positioned intermediate said opaque layer comprising titanium dioxide and the photosensitive silver halide layer next adjacent thereto.
 10. A composite photographic diffusion transfer process film unit as defined in claim 1 wherein said opacifying agent is actinic radiation reflective.
 11. A composite photographic diffusion diffusiom transfer process film unit as defined in claim 10 wherein said opacifying agent comprises an inorganic reflecting pigment and at least one optical filter agent.
 12. A composite photographic diffusion transfer process film unit as defined in claim 11 wherein said opacifying agent including said inorganic reflecting pigment and said optical filter agent is disposed in said processing composition and comprises an inorganic reflecting pigment dispersion including at least one optical filter agent at a pH above the pKa of said optical filter agent in a concentration effective to provide a layer exhibiting an optical transmission density > about six density units and an optical reflection density < about one and said film unit includes means for reducing the pH of the processing composition from a pH above the pKa of the filter agent to a pH below the pKa of the filter agent subsequent to substantial dye transfer image formation in said first and said second dyeable polymeric layers.
 13. A composite photographic diffusion transfer process film unit as defined in claim 12 wherein said optical filter agent is a pH sensitive dye.
 14. A composite photographic diffusion transfer process film unit as defined in claim 11 wherein said optical filter agent is a pH-sensitive dye disposed in a layer intermediate said second dyeable polymeric layer and next adjacent photosensitive silver halide layer at a pH below the pKa of said pH-sensitive dye and said processing composition possesses a pH above the pKa of said pH-sensitive dye.
 15. A composite photographic diffusion transfer process film unit as defined in claim 11 wherein said inorganic reflecting pigment is disposed in a layer intermediate said second dyeable polymeric layer and next adjacent photosensitive silver halide layer in a concentration effective to mask diffusion transfer process dye image-forming material associated with said photosensitive silver halide layer and insufficient to prevent exposure of said photosensitive silver halide layer by radiation incident on said second dimensionally stable trasparent layer and actinic to said photosensitive layer.
 16. A composite photographic diffusion transfer process film unit as defined in claim 15 wherein said layer containing said inorganic reflecting pigment includes at least an optical filter agent at a pH below the pKa of said agent and said processing composition possesses a pH above the pKa of said optical filter agent.
 17. A composite photographic diffusion transfer process film unit as defined in claim 15 wherein said means for providing said processing composition is adapted to distribute said processing composition intermediate said inorganic reflecting pigment layer and the photosensitive silver halide layer next adjacent thereto and said processing composition includes opacifying agent in a concentration effective upon distribution in a layer intermediate said pigment layer and said next adjacent photosensitive layer to prevent exposure of said photosensitive silver halide layer during processing in the presence of radiation actinic thereto incident on said opacifying agent layer.
 18. A composite photographic diffusion transfer process film unit as defined in claim 17 wherein said inorganic reflecting pigment is present in a concentration effective to mask opacifying Agent distributed intermediate said reflecting pigment layer and the photosensitive layer next adjacent thereto.
 19. A composite photographic diffusion transfer process film unit as defined in claim 1 wherein said means for providing said processing composition comprises rupturable container means retaining said processing composition extending transverse an edge of said film unit to effect, upon application of compressive pressure to the container means, discharge of said container means processing composition contents intermediate said second dyeable layer and the photosensitive silver halide layer next adjacent.
 20. A composite photographic diffusion transfer process film unit as defined in claim 1 wherein said diffusion transfer process dye image-forming material is a dye which is a silver halide developing agent.
 21. A composite photographic diffusion transfer process film unit as defined in claim 20 wherein said dye is soluble and diffusible at a first pH and substantially nondiffusible at a second pH.
 22. A composite photographic diffusion transfer process film unit as defined in claim 1 including intermediate said opaque layer and said second dyeable layer at least two selectively sensitized silver halide layers each having associated therewith a dye image-forming material adapted to provide a dye image of predetermined color as a function of the photoexposure of its associated silver halide layer.
 23. A composite photographic diffusion transfer process film unit as defined in claim 22 wherein each of said selectively sensitized silver halide layers of said each film unit possesses predominant spectral sensitivity to separate regions of the spectrum and said dye image-forming material associated with each of said silver halide layers is adpated to provide a dye transfer image possessing a spectral absorption range subsequent to processing substantially complementary to the predominant sensitivity range of its associated silver halide layer.
 24. A composite photographic diffusion transfer process film unit as defined in claim 23 wherein said processing composition and said color film units each include means for converting the pH of said processing composition, subsequent to substantial diffusion dye image-forming materials to said receiving layer, from a first alkaline process pH to a second pH less than said first pH at which the dye transfer image provided by said dye image-forming materials exhibits increased stability.
 25. A composite photographic diffusion transfer process film unit as defined in claim 24 wherein said selectively sensitized silver halide layers include, as essential layers, a red-sensitive silver halide emulsion layer having associated therewith a diffusion transfer process cyan dye image-forming material, a green-sensitive silver halide emulsion layer having associated therewith a diffusion transfer process magenta dye image-forming material and a blue-sensitive silver halide emulsion layer having associated therewith a diffusion transfer process yellow dye image-forming material.
 26. A process for providing composite photographic diffusion transfer process dye images which comprises, in combination, the steps of: a. exposing to incident actinic radiation a photographic diffusion transfer process film unit which comprises a plurality of layers including, in order, a first dimensionally stable transparent layer; a first dyeable layer adapted to receive diffusion transfer process dye image-forming material diffusing thereto; an opaque layer; a photosensitive silver halide layer having associated therewith a diffusion transfer process dye image-forming material; a second dyeable layer adapted to receive diffusion transfer process dye image-forming material diffusing thereto; and a second dimensionally stable transparent layer, said exposing actinic radiation incident on said second dimensionally stable transparent layer; b. providing opacifying agent intermediate said second dyeable layer and the photosensitivE silver halide layer next adjacent; c. contacting the photoexposed silver halide layer with a processing composition and effecting thereby formation of an imagewise distribution of mobile dye image-forming material as a function of the point-to-point degree of silver halide layer photoexposure; d. transferring, by diffusion, at least a portion of said imagewise distribution of mobile dye image-forming material to said first and said second dyeable layers adapted to receive dye image-forming material diffusing thereto to thereby provide to each of said first and said second dyeable layers a dye image in terms of said imagewise distribution; and e. maintaining said film unit intact subsequent to processing.
 27. A process for providing composite photographic diffusion transfer process dye images as defined in claim 26 including the step of converting the pH of said film unit, subsequent to substantial dye image formation in said first and said second dyeable layers, from a first processing pH provided by said processing composition to a second pH at which said dye images exhibit increased stability.
 28. A process for providing composite photographic diffusion transfer process dye images as defined in claim 27 wherein said dye image-forming material comprises a dye which is a silver halide developing agent and is soluble and diffusible in said processing composition at said first pH as a function of the photoexposure of said film unit and is substantially nondiffusible at said second pH.
 29. A process for providing composite photographic diffusion transfer process dye images as defined in claim 27 wherein said first processing pH is an alkaline pH and said second pH is > about one pH unit lower than said first pH.
 30. A process for providing composite photographic diffusion transfer process dye images as defined in claim 27 wherein said opacifying agent includes at least one optical filter agent possessing a pKa above said second pH and below said first pH.
 31. A process for providing composite photographic diffusion transfer process dye images as defined in claim 30 wherein said opacifying agent includes an inorganic reflecting pigment.
 32. A process for providing composite photographic diffusion transfer process dye images as defined in claim 26 wherein each of said opacifying agent and said opaque layer reflect incident visible radiation.
 33. A process for providing composite photographic diffusion transfer process dye images as defined in claim 32 which comprises, in combination, the steps of: a. exposing to incident actinic radiation a composite photographic film unit which comprises a plurality of sequential layers including a first dimensionally stable layer transparent to incident actinic radiation; a first alkaline solution dyeable layer; an alkaline solution permeable opaque layer comprising an inorganic light-reflecting pigment; at least two selectively sensitized silver halide emulsion layers possessing predominant spectral sensitivity to separate regions of the visible electromagnetic spectrum and a dye which is a silver halide developing agent and is soluble and diffusible in aqueous alkaline processing composition as a function of photoexposure of the film unit, at a first pH, associated with each of the silver halide emulsion layers and possessing spectral absorption range, subsequent to processing, substantially complementary to the predominant sensitivty range of its associated silver halide emulsion layers; a second alkaline solution dyeable layer; a second dimensionally stable layer transparent to incident actinic radiation; at least one layer possessing neutralizing capacity effective to reduce the alkaline processing composition possessing the first pH to a second pH at which the dyes are substantially nondiffusible positioned intermediate at least one of the first and second dimensionally stable transparent layers and next adjacent essential layer; and means for securing the layers in substantially fixed relationship; a rupturable container retaining an alkaline processing composition possessing the first pH and retaining substantially uniformly dispersed therein an inorganic light-reflecting pigment and at least one optical filter agent, substantially nondiffusible from the processing composition and possessing a pKa below the first pH and above the second pH, exhibiting spectral absorption substantially complementary to a predominant sensitivity range of the selectively sensitized silver halide emulsion layers, at the first pH, and the light-reflecting pigment and optical filter agent present in a quantity sufficient, upon distribution of the alkaline processing composition possessing the first pH as a layer intermediate the second dyeable layer and next adjacent selectively sensitized silver halide emulsion layer, to substantially prevent transmission therethrough of incident exposure radiation actinic to the silver halide emulsion layers and the rupturable container is positioned and extends transverse an edge of the photosensitive element to effect discharge of the container''s alkaline processing composition intermediate the second dyeable layer and the selectively sensitized silver halide emulsion layer next adjacent; b. effecting discharge of the container''s alkaline processing composition intermediate the second dyeable layer and the photosensitive silver halide emulsion layer next adjacent; c. effecting thereby development of each of the selectively sensitized silver halide emulsions; d. forming thereby imagewise distributions of mobile dye as a function of development; e. transferring, by diffusion, at least a portion of each of the imagewise distributions of mobile dye to each of the first and second dyeable polymeric layers to provide to each a dye image in terms of the imagewise distributions; f. transferring, by diffusion, subsequent to substantial dye transfer image formation, a sufficient portion of the ions of the alkaline processing composition to the neutralizing layer to thereby reduce the alkalinity of the composition from the first pH at which the dyes associated with the silver halide emulsions are soluble and diffusible as a function of photoexposure of the film unit and above the pKa of the pH-sensitive dye to the second pH below the pKa of the pH-sensitive dye and at which the dyes associated with the silver halide emulsions are substantially nondiffusible; and g. maintaining the composite structure intact subsequent to processing.
 34. A process for providing composite photographic diffusion transfer process dye images as defined in claim 33 which comprises, in combination, the steps of: a. exposing to incident actinic radiation a photographic film unit which comprises a composite structure containing, as essential layers, in sequence, a first dimensionally stable alkaline solution impermeable transparent layer; a first alkaline solution dyeable polymeric layer; an alkaline solution permeable inorganic light-reflecting pigment layer comprising titanium dioxide; an alkaline solution permeable opaque layer comprising carbon black; a red-sensitive silver halide emulsion layer having associated therewith cyan dye; a green-sensitive silver halide emulsion layer having associated therewith magenta dye; a blue-sensitive silver halide emulsion layer having associated therewith yellow dye, each of the cyan, magenta and yellow dyes being silver halide developing agents and being soluble and diffusible, in alkali, at a first pH; a second alkaline solution dyeable polymeric layer; a second dimensionally stable alkaline solution impermeable transparent layer; a polymeric layer containing sufficient acidifying capacity to effect reduction of a processing composition having the first pH at which the cyan, magenta and yellow dyes are soluble and diffusible to a second pH at which the dyes are substantially nondiffusible positioned intermediate at least one of said dimensionallY stable transparent layers and next adjacent dyeable layer; and means securing said layers in substantially fixed relationship; and a rupturable container retaining an aqueous alkaline processing composition having the first pH and containing substantially uniformly disposed therein titanium dioxide and at least one pH-sensitive dye substantially nondiffusible from said processing composition and possessing a pKa below the first pH and above the second pH, the titanium dioxide and the pH-sensitive dyes taken together present in a quantity sufficient, upon distribution of the aqueous alkaline processing composition possessing the first pH as a layer intermediate the second dyeable polymeric layer and the blue-sensitive silver halide emulsion layer, to provide a layer possessing an optical transmission density > about six density units with respect to incident radiation actinic to the silver halide emulsion layers and an optical reflection density < about one density unit with respect to incident visible radiation, and the container is fixedly positioned and extends transverse a leading edge of the photosensitive element to effect upon application of compressive force unidirectional discharge of the container''s aqueous alkaline processing composition possessing the first pH intermediate the second dyeable polymeric layer and blue-sensitive silver halide emulsion layer; b. applying compressive force to the rupturable container to effect unidirectional discharge of the container''s aqueous alkaline processing composition intermediate the second dyeable polymeric layer and the blue-sensitive silver halide layer; c. effecting thereby development of the red-, green-and blue-sensitive silver halide emulsion; d. immobilizing the cyan, magenta and yellow dyes as a result of development of their associated silver halide emulsion; e. forming thereby an imagewise distribution of mobile cyan, magenta and yellow dye as a function of the point-to-point degree of exposure of their associated silver halide emulsion; f. transferring, by diffusion, at least a portion of each of the imagewise distributions of mobile cyan, magenta and yellow dye to each of the alkaline solution permeable polymeric layers dyeable by said dyes to provide thereto a multicolor dye image; g. transferring, by diffusion, subsequent to substantial dye transfer, a sufficient portion of the ions of the aqueous alkaline processing composition to the polymeric acid layer to thereby reduce the alkalinity of the film unit from the first pH, above the pKa of the pH-sensitive dyes, at which the cyan, magenta and yellow image dyes are soluble and diffusible to a second pH, below the pKa of the pH-sensitive dyes, at which the cyan, magenta and yellow image dyes are substantially nondiffusible; and h. maintaining the composite structure intact subsequent to processing. 